I must say I like it :P but also I think that this will not be the fastest solution for every variation of initial list/sublist. I suppose more answers will appear and someone will make some comparisons :p
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KubaSep 15 '13 at 23:12

@Kuba It probably won't be the fastest, but it should be reasonably efficient, since it's not walking through list multiple times.
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rm -rf♦Sep 15 '13 at 23:15

My apologies but I must condemn this method. I am well known for my fixation on terse code but I cannot excuse this; it is exactly the kind of application that I lamented in Why is there no PositionFunction in Mathematica?. (I mean no offense to you by this; it's nice clean code but I consider it a "siren song" that new users must be warned against.)
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Mr.Wizard♦Sep 16 '13 at 7:18

@Mr.Wizard I didn't say it was efficient, but I do think it's the clearest statement yet of what is to be done. Perhaps its best use would be in a comment, along with something like "that's what we need, and here's how we get it efficiently."
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Ray KoopmanSep 16 '13 at 12:18

I agree that it is the clearest code. I think it deserves more than a comment. (You'll notice that I did not down-vote this answer.) I suppose I was overly harsh yesterday, but at the same time I think there is a genuine need for a warning with such things. I think what I'll do, if I have time, is provide timings for the methods posted; then people can see for themselves how these behave without me unfairly singling out your method for criticism.
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Mr.Wizard♦Sep 16 '13 at 16:58

BinCounts is/was quite slow in v7; how does it compare to Tally in v9?
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Mr.Wizard♦Sep 16 '13 at 2:43

@Mr.Wizard been offline for a few days. In my experience BinCounts is usually slow -- I usually look for alternatives if speed is important -- but offered it here as an alternative. Whether it is viable depends on the real data to be used.
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Mike HoneychurchSep 20 '13 at 23:15

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